1. Technical Field
The invention relates to image capture and, particularly, to an image capture device providing image previews with uniform brightness and a method thereof.
2. Description of the Related Art
In general, charge-coupled device (CCD) systems such as video cameras or digital still cameras include a CCD image sensor and a lens module. The CCD image sensor repeats readout of an image signal generated thereby as consecutive preview images at a predetermined rate, such as 30 frames per second (FPS), the system being National Television System Committee (NTSC)-compliant. Problems may result in a CCD system when capture is performed under fluorescent lighting conditions operated at a commercial frequency of 50 Hertz (Hz). As shown in FIG. 5, a graph illustrating autofocus of a common image capture device, horizontal axis represents preview time in milliseconds (ms) and the vertical axis brightness in lux (lx) of such a fluorescent lighting condition. During preview, the CCD image sensor is exposed at a uniform exposure of Yms to acquire consecutive preview images corresponding to different focus conditions of the lens module, such as a focus lens thereof positioned at different focus positions P1˜Pk (in FIG. 5, k being a natural number). As shown, brightness values L1˜Lk of the consecutive preview images are not equal, since the sampling rate of the CCD image sensor (30 Hz) is not compatible with the illuminative frequency of 50 Hz, and flicker results. This can decrease autofocus accuracy if a contrast measurement method is used.
Therefore, it is desirable to provide an image capture device and method thereof, which can overcome the limitations described.